From EP 0 035 290 A1 a generic piston for an internal combustion engine is known, having an upper part consisting of ferrous material and a lower part connected therewith via conventional means, wherein there is situated on the underside of the upper part a ring resting on the corresponding surface of the lower part, which ring encloses both the radial inner boundary of the cooling duct, which is open to the connecting plane, in the upper part, and also a central cooling chamber in the upper part, connected with the cooling duct via radially arranged coolant bores and open to the connecting plane. In order to be able to bring about an improvement to the cooling effect in the hottest regions of the upper part, and an equalizing of the temperature distribution in the ring area, the upper wall region of the cooling duct is coated with a highly thermally conductive material.
Modern pistons are usually cooled for reaching high engine performances and have here a substantially ring-shaped cooling duct running between a piston upper part and a piston lower part. In order to be able to discharge the thermal energy occurring in the combustion chamber, the heat occurring in the piston upper part is discharged via the cooling fluid, for example oil, flowing in the cooling duct. However, the heat distribution here is very variable in the region of the upper part, whereby not only do thermal stresses occur within the piston, but also an optimum heat removal through the cooling fluid flowing in the cooling duct is at least made difficult.